1. Field of the Invention
The present invention generally relates to a scroll type refrigerant compressor provided with a stationary scroll unit stationarily arranged in a housing and a movable scroll unit cooperating with the stationary scroll unit so as to compress refrigerant gas, and more particularly, relates to a scroll type refrigerant compressor with means for preventing mechanical breakage of the housing.
2. Description of the Related Art
U.S. Pat. No. 4,824,346 discloses a typical scroll type refrigerant compressor. The scroll type refrigerant compressor is provided with a stationary scroll unit fixedly encased in a housing means, and a movable scroll unit orbiting in the housing means so as to compress refrigerant gas in cooperation with the stationary scroll unit. The stationary scroll unit includes a stationary spiral member and an end plate member fixedly attached to an end of the spiral member and to the housing means. The stationary spiral member is formed as a wall member extending spirally along an involute curve with respect to a given point, i.e., a center of the stationary spiral member.
The movable scroll unit includes a movable spiral member engaged with the stationary spiral member and a movable end plate fixed to an end of the movable spiral member on the side axially opposite to the end plate member of the stationary scroll unit. The movable spiral member which is also formed as a wall member extending spirally along an involute curve with respect to a given point, i.e., a center of the movable spiral member is arranged so as to be circumferentially shifted the stationary scroll member by a given angle. Thus, when the movable scroll unit orbits along a predetermined circular path with respect to the stationary scroll unit, the refrigerant gas is pumped from a suction chamber arranged in a radially outer portion of the stationary and movable spiral members into a closed compressing chamber formed between the stationary and movable scroll members. The compressing chamber is shifted from the outer portion of the stationary and movable spiral members toward the center thereof in relation to the orbiting motion of the movable spiral member, and during the shifting of the compressing chamber, the volume thereof is gradually reduced so as to compress the refrigerant gas. When the compressing chamber reaches the center of the two spiral members, the compressed refrigerant gas is discharged from the compressing chamber toward a discharge chamber through a discharge port centrally formed in the end plate member of the stationary scroll unit.
Further, the stationary scroll unit including the stationary spiral member is made of aluminum alloy so as to reduce the weight thereof. In addition, the housing means in which the stationary scroll unit is encased is usually made of aluminum alloy to reduce the overall weight of the compressor.
The stationary scroll unit and the encasing housing means may either be separate members as shown in Japanese Unexamined Japanese Patent Publication (Kokai) No. 61-38189 or may be a single light and small-diameter integral member made of aluminum alloy as disclosed in Japanese Unexamined Patent publication (Kokai) No. 3-134287.
In the above-described conventional scroll type refrigerant compressor, the movable spiral member of the movable scroll unit moves along a predetermined circular path, that is, the movable scroll unit orbits along the predetermined path under such a condition that the turning of the movable spiral member about the center thereof is prevented. When the movable spiral member orbits maintaining an engagement between the stationary and movable spiral members, seizure of the stationary and movable spiral members there may occur due to strong contact of the two members during continuous running of the compressor, and accordingly, the two stationary and movable spiral members may be mechanically damaged. Thus, a piece or pieces of the broken members may enter between the outer wall of the movable spiral member and the inner wall of the housing means so as to jam the movable scroll unit to thereby eventually crack the housing means which is made of a breakable material such as aluminum alloy. The breakage of the housing means of the scroll type refrigerant compressor permits the leakage of Freon gas used as refrigerant gas into the atmosphere, and results in an undesirable problem from the viewpoint of environmental protection.